Fathom is an multiplayer online game similar to Mastermind. You try to guess the squence of the four colored balls in as few guesses as possible. You receive clues for each guess. The clue lets you know how many balls you have in the correct spot, how many you have that are the correct color but in the wrong spot, and how many balls will not be used to complete the code. You will need The Lobby from www.tams11.com in order to play online.